U.S. Pat. No. 6,354,237 discloses a trim tab control system in which four buttons or switches are provided for the marine operator in which the operator can select to raise the bow, raise the stern, raise the port side of the boat, or raise the stern side of the boat in relative terms, and the system will automatically position the trim tabs to most efficiently achieve the operator's demanded change in position of the marine vessel.
U.S. Pat. No. 6,583,728 discloses a trim tab monitoring circuit which receives a signal that is representative of a voltage potential across a stator winding of a motor which is attached to the trim tab. This signal is passed through a high pass filter to remove the DC component of the signal, amplified, and passed through a low pass filter to remove certain high frequencies components of the signal. A zero crossing detector is used to discern individual pulses which are then received by a counter that provides a single output pulse for a predetermined number of input pulses. The series of output pulses from the counter are conditioned and, in conjunction with a direction sensor, provided to an up/down counter controller that provides digital signals to a signal output circuit. The signal output circuit provides a DC voltage output to a display and the DC output voltage is representative of the position of the trim tab.
U.S. Pat. No. 7,188,581 discloses a marine drive and a marine vessel and drive combination having a trim tab with a forward end pivotally mounted to a marine propulsion device.
Each of the above patents is hereby incorporated herein by reference in its entirety.